Brushes that are in use today, and in particular toothbrushes, are commonly made entirely from plastic materials. The bristles of the brush generally comprise a high-grade polyamide, processed by extrusion to form thin fibers, which are then stretched and thermally stabilized. The body of the brush, however, is typically made from a lesser grade plastic that is injection molded. The head area of the brush body must be so dimensioned as a function of the nature of the fixing of the bristles, that the latter, which are optionally combined in bundles, are adequately firmly anchored.
For toothbrushes, the head area must also be as flat as possible so as to take up as little space in the oral cavity as possible, or so as to be able to utilize the existing space with substantially extended bristles. The handle of the body must be dimensionally stable and rigid. It is also desirable for the head to be somewhat flexible with respect to the handle in order to damp the pressing force during the cleaning of the teeth, or to otherwise control the pressure. Therefore, a smaller cross-section neck, which gives the brush body a certain flexibility, is generally provided between the head and the handle. The constriction resulting from the neck also fulfills an ergonomic function, in order to be able to guide the toothbrush in the desired cleaning movements with the mouth closed.
The thermoplastics generally used for toothbrushes only very inadequately fulfill these opposing requirements. This more particularly applies for the desired flexibility between the head and the handle and also the desired small cross-section at the head and neck. Therefore, the cross-section in the area of the head and neck must be relatively large, so as not to break during use or any other extraordinary stressing. The same applies with respect to the head, because the latter is cross-sectionally weakened due to the fastening measures for the bristle bundles, particularly if as is normally the case, the bundles are mechanically or thermally anchored or injected into holes in the head. Also when welding the bundles onto the head material, weakening may occur, because the surface molecular structure on the head may be disadvantageously modified.
Although many toothbrushes on the market today claim to have flexible neck designs, in fact most of these brushes are not truly flexible. Some merely use a twisted neck pattern or a narrow neck design to create a visual impression of flexibility.
In addition, previous attempts to achieve a desired flexibility in the head with respect to the handle, or in the head alone, have involved multi-component brushes, which have inserted springs or distinct thermoplastic elastomer sections inserted in the neck area between the head and the handle. See, e.g., Japanese Kokai application H9-19323 to Shiseido, published on Jan. 21, 1997; and International Publication Nos. WO 92/17092-3, published Oct. 15, 1992. Such brushes have limited flexibility, since they can only bend at the hinge areas or according to the distribution of the separate elastomer sections. In addition, they may require greater attention to manufacturing tolerances and may be more expensive to manufacture than a one piece brush.
Yet another proposed solution is to provide a brush body made of an elastomer mixed with a foaming agent in the area of the handle, and being substantially solid in the area of the smaller cross-section of the head. See U.S. Pat. No. 5,815,874 to Weihrauch on Oct. 6, 1998.
However, there remains a desire to provide a cost-effective, one-piece brush that has a true, multi-directional bending capability. None of the existing art provides all of the advantages and benefits of the present invention.